Since ancient "Wise Men" first looked to the sky for guidance millenia ago, astrology has asserted that there is some relationship between celestial phenomena and human life, growth, and life events. There have been practicing astrologers, and presumably their clients, in every civilization in time. Today in the United States there are estimated to be 20,000 professional astrologers, approximately 5,000 of those being members of the American Federation of Astrologers. There are two basic areas of astrology to consider. The first relates to the objective extraction and display of astronomical information relating to the movement of the planets as seen from Earth, from which information inferences may be drawn. (In this context, the term "planets" will also be taken to include the Sun and the Moon, but not Earth.) The second is more subjective and relates to an interpretation of various features of the data as they relate to an individual's life experience. Clearly, since data are necessary for an interpretation, these areas are not unrelated. Moreover, depending on the way the information is formatted, different types of interpretations may be available and may further dictate new ways of extracting and formatting data.
Even the most superficial student of the subject (one who has gleaned his total knowledge from a reading of the daily astrology column in the newspaper) is made to recognize that a person's birthdate is somehow significant. Elaborating on this, taking the geocentric positions of the planets in relation to the fixed stars on the ecliptic and in relation to each other (the "aspects") at a given moment in time provides a basic natal horoscope applicable to all people born at that particular time, regardless of location. For this purpose, the precise moment of birth tends often not to be critical.
However, it has also been found that the orientation of the planets with respect to the local horizon is important, so that the precise moment of birth and geographical location become significant. In particular, the ascendant (ASC), the descendant (DSC), the midheaven or upper meridian transit (MH), and the lower meridian transit, called the Imum Coeli (IC) are accepted as being the most powerful positions in the horoscope. Planetary influences tend to be the most powerful if the planet was at one of the aforementioned zones of power, called the "angles" of the chart. A person born with a planet near one of these angles tends to exhibit strongly the qualities associated with the planet. For example, if Mars was at such a position at the person's birth, that person is likely to show aggressive tendencies. The character of the individual planets and their angularities are generally well known to those versed in the astrological arts.
Since the Earth is constantly rotating, the relation of the local horizon to the ecliptic and the planets thereon is constantly varying, temporally and geographically. For example, when the sun is rising in the eastern United States, it is directly overhead in western Europe. While a person is not able to change the time and place of his birth, and thus his natal horoscope, it has been found that a particular planetary influence tends to be maximized at locations on Earth where that particular planet was in fact angular at the moment of the individual's birth. If one moves to a new location, a "relocation" horoscope must be set up, being determined as if the person had been born there in the first place. The aspects, i.e. the relationships of the planets to one another and to the ecliptic, do not change, but the angles, i.e. the relationship of the planets to the horizon and the meridian, do change. Put another way, by traveling, a person can to some extent adjust his horoscope so that it operates as if he been born at a different time of the day. Thus, for example, a person who was born at a time and place when the planet Mars was not angular may find that when he travels to places on earth where Mars was in fact angular when he was born, he will have a greater tendency to become involved in aggressive or violent (Mars-like) activities. Similarly, a person may find that he undergoes life-threatening experiences, when he travels to places where Pluto was angular at birth as Pluto has long been associated with such events.
One of the most useful ways of presenting information relative to such potential relocations is to provide a map of the world and plot thereon loci of planetary angularity. For example, the MH and IC lines for each planet are lines of constant longitude, being spaced by 180.degree. of longitude. The ASC and DSC lines are segments of a smooth curve. Services for the preparation of such maps, customized for a particular individual, are commercially available, being provided under the registered service mark Astro*Carto*Graphy.
While such a map provides information regarding zones of potential planetary power, the information thereon does not have a particular time frame since it is defined solely by the moment of birth. However, it is well established that astrology is a dynamic system, with the positions of celestial bodies at birth being the starting point against which various cycles that are assumed to relate to human growth cycles are measured. Metaphorically, at the moment of birth, a series of clocks having differing periodicities begin running.
Broadly, there are two commonly accepted ways to account for the planetary motion and the resulting changes over time, namely transits and progressions. Transitting information for a given moment in time is conceptually simpler, reflecting the actual positions of the planets at that moment, especially as they relate to natal planetary positions. Progressions, on the other hand, involve various symbolic advances of the planets and angles tied into astronomically relevant ratios and cycles of human maturation and consciousness. The various types of commonly used progressions are related to and derive from the interaction of the rotation of the Earth about its axis and the orbit of the Earth around the Sun. In a "primary" progression, the planets' apparent motions along the diurnal semi-arc arising from the rotation of the Earth are taken as the key motion; approximately four minutes of such rotation is equated to one year of life. In a "secondary" progression, the planets' own discrete motions along the ecliptic after birth are taken as a key, and related in the ratio 1:365.25, or a day to a year. For example, when a person is 40 years old, his secondarily progressed chart would reflect the planetary positions as they actually were 40 days after his birth. In a "solar arc" progression, the Sun's motion is taken as the key; all angles and planetary positions are advanced at the ratio of one day's solar motion equal to one year.
The use of progressions and transits in relocation work is rarely done since the calculations are formidably cumbersome.